Methods useful in the synthesis of halichondrin b analogs

ABSTRACT

In general, the present invention features improved methods useful for the synthesis of analogs of halichondrin B, such as eribulin and pharmaceutically acceptable salts thereof (e.g., eribulin mesylate).

The invention relates to methods useful in the synthesis of analogs ofhalichondrin B, in particular ER-086526, referred to under its genericname eribulin throughout the following specification.

BACKGROUND OF THE INVENTION

Eribulin (marketed under the trade name HALAVEN® as eribulin mesylate),a nontaxane microtubule dynamics inhibitor, is a structurallysimplified, synthetic analog of the marine natural product halichondrinB. Methods for the synthesis of eribulin and other halichondrin Banalogs are described in U.S. Pat. Nos. 6,214,865, 6,365,759, 6,469,182,7,982,060, and 8,148,554, the syntheses of which are incorporated hereinby reference. New methods for the synthesis of halichondrin B analogs,in particular eribulin and eribulin mesylate, are desirable.

SUMMARY OF THE INVENTION

In general, the present invention features improved methods useful forthe synthesis of analogs of halichondrin B, such as eribulin andpharmaceutically acceptable salts thereof (e.g., eribulin mesylate).

In one aspect, the invention features a method of preparing anintermediate in the synthesis of eribulin including reacting a compoundhaving formula (I):

wherein each of R¹, R², R³, R⁴, and R⁵ is independently a silyl group(e.g., trimethylsilyl (TMS), triethylsilyl (TES), t-butyldimethylsilyl(TBS), t-butyldiphenylsilyl (TBDPS), triisopropylsilyl (TIPS), ortriphenylsilyl (TPS)), with a fluoride source (e.g., tetrabutylammoniumfluoride) in a solvent including an amide, e.g., a N,N C1-C6 dialkylC1-C6 alkyl amide or N C1-C6 alkyl C2-C6 lactam, such asN,N-dimethylacetamide (e.g., as a mixture of tetrahydrofuran andN,N-dimethylacetamide), N,N-dimethylformamide, N-methyl 2-pyrrolidone,N,N-diethylacetamide, or N,N-dimethylpropionamide, to produce theintermediate ER-811475:

ER-811475 may be produced in a mixture with its C12 stereoisomer,ER-811474:

The method may further include adding a mixture of acetonitrile andwater to increase the yield of ER-811475.

In some embodiments, each of R¹, R², R³, R⁴, and R⁵ ist-butyldimethylsilyl (TBS).

The invention further features a method of preparing an intermediate inthe synthesis of eribulin including reacting (e.g., in ethanol)ER-811475 with a conjugate acid of imidazole (e.g., imidazolehydrochloride) to produce the intermediate ER-076349:

ER-811475 can be produced by any of the methods provided herein.

In another aspect, the invention features a method of preparing anintermediate in the synthesis of eribulin. This method includes reacting(e.g., in acetonitrile) ER-076349 with a sulfonylating reagent, e.g.,tosyl chloride, in the presence of a metal catalyst (e.g., dibutyltinoxide) to produce the intermediate:

wherein R₆ is sulfonyl, e.g., ER-082892. The reacting may occur above 0°C. ER-076349 can be produced by any of the methods provided herein. Themethods may also include addition of a base, e.g., a C1-6 trialkylamine,such as triethylamine or N,N-diisopropylethylamine.

The invention also features a method of producing eribulin. This methodincludes producing intermediate ER-811475 by any one of the foregoingmethods, ketalizing ER-811475 to produce the intermediate ER-076349, andaminating ER-076349 to produce eribulin (ER-086526):

The step of ketalizing ER-811475 may include converting ER-811475 toER-076349 according to any of the methods provided herein. The step ofaminating ER-076349 to produce eribulin may include converting ER-076349to ER-082892 according to any of the methods provided herein.

The invention further features an alternative method of producingeribulin. This method includes producing intermediate ER-076349 by anyone of the foregoing methods and aminating ER-076349 to produceeribulin. The step of aminating ER-076349 to produce eribulin mayinclude converting ER-076349 to ER-082892 according to any of themethods provided herein.

In a further aspect, the invention features yet another method ofproducing eribulin. This method includes producing intermediateER-082892 by any of the methods provided herein and aminating ER-082892to produce eribulin.

Any method of producing eribulin may further include salifying eribulinto produce a pharmaceutically acceptable salt of eribulin (e.g.,eribulin mesylate).

The invention further features a method of manufacturing apharmaceutical product including eribulin or a pharmaceuticallyacceptable salt thereof (e.g., eribulin mesylate). This method includesproducing or directing the production of eribulin or a pharmaceuticallyacceptable salt thereof by any one of the foregoing methods andprocessing or directing the processing of eribulin or a pharmaceuticallyacceptable salt thereof into a pharmaceutical product including eribulinor a pharmaceutically acceptable salt thereof, thereby manufacturing apharmaceutical product including eribulin or a pharmaceuticallyacceptable salt thereof.

The processing step can include one or more of formulating eribulin or apharmaceutically acceptable salt thereof (e.g., eribulin mesylate);processing eribulin or a pharmaceutically acceptable salt thereof into adrug product; combining eribulin or a pharmaceutically acceptable saltthereof with a second component (e.g., an excipient or pharmaceuticallyacceptable carrier); lyophilizing eribulin or a pharmaceuticallyacceptable salt thereof; combining a first and second batch of eribulinor a pharmaceutically acceptable salt thereof to provide a third largerbatch; disposing eribulin or a pharmaceutically acceptable salt thereofinto a container (e.g., a gas or liquid tight container); packagingeribulin or a pharmaceutically acceptable salt thereof; associating acontainer including eribulin or a pharmaceutically acceptable saltthereof with a label; and shipping or moving eribulin or apharmaceutically acceptable salt thereof to a different location.

For any of the following chemical definitions, a number following anatomic symbol indicates the total number of atoms of that element thatare present in a particular chemical moiety. As will be understood,other atoms, such as hydrogen atoms, or substituent groups, as describedherein, may be present, as necessary, to satisfy the valences of theatoms. For example, an unsubstituted C2 alkyl group has the formula—CH₂CH₃. A reference to the number of oxygen, nitrogen, or sulfur atomsin a heteroaryl group only includes those atoms that form a part of aheterocyclic ring.

By “alkyl” is meant a straight or branched chain saturated cyclic (i.e.,cycloalkyl) or acyclic hydrocarbon group of from 1 to 12 carbons, unlessotherwise specified. Exemplary alkyl groups include C1-C8, C1-C6, C1-C4,C2-C7, C3-C12, and C3-C6 alkyl. Specific examples include methyl, ethyl,1-propyl, 2-propyl (i.e., isopropyl), 2-methyl-1-propyl (i.e.,iso-butyl), 1-butyl, 2-butyl, 1,1-dimethylethyl (i.e., tert-butyl) andthe like. Unless otherwise noted, alkyl groups, used in any contextherein, are optionally substituted with halogen, alkoxy, aryloxy,arylalkyloxy, oxo, alkylthio, alkylenedithio, alkylamino,[alkenyl]alkylamino, [aryl]alkylamino, [arylalkyl]alkylamino,dialkylamino, silyl, sulfonyl, cyano, nitro, carboxyl, or azido.

By “alkylamino” is meant —NHR, wherein R is alkyl. By“[alkenyl]alkylamino” is meant —NRR′, wherein R is alkyl, and R′ isalkenyl. By “[aryl]alkylamino” is meant —NRR′, wherein R is alkyl, andR′ is aryl. By “[arylalkyl]alkylamino” is meant —NRR′, wherein R isalkyl, and R′ is arylalkyl. By “dialkylamino” is meant —NR₂, whereineach R is alkyl, selected independently.

By “alkylene” is meant a divalent alkyl group. Alkylene groups, used inany context herein, are optionally substituted in the same manner asalkyl groups. For example, an unsubstituted C1 alkylene group is —CH₂—.

By “alkylenedithio” is meant —S-alkylene-S—.

By “alkylthio” is meant —SR, wherein R is alkyl.

By “alkenyl” is meant a straight or branched chain cyclic or acyclichydrocarbon group of, unless otherwise specified, from 2 to 12 carbonsand containing one or more carbon-carbon double bonds. Exemplary alkenylgroups include C2-C8, C2-C7, C2-C6, C2-C4, C3-C12, and C3-C6 alkenyl.Specific examples include ethenyl (i.e., vinyl), 1-propenyl, 2-propenyl(i.e., allyl), 2-methyl-1-propenyl, 1-butenyl, 2-butenyl (i.e., crotyl),and the like. Alkenyl groups, used in any context herein, are optionallysubstituted in the same manner as alkyl groups. Alkenyl groups, used inany context herein, may also be substituted with an aryl group.

By “alkoxy” is meant —OR, wherein R is alkyl.

By “aryl” is meant a monocyclic or multicyclic ring system having one ormore aromatic rings, wherein the ring system is carbocyclic orheterocyclic. Heterocyclic aryl groups are also referred to asheteroaryl groups. A heteroaryl group includes 1 to 4 atoms selectedindependently from O, N, and S. Exemplary carbocyclic aryl groupsinclude C6-C20, C6-C15, C6-C10, C8-C20, and C8-C15 aryl. A preferredaryl group is a C6-10 aryl group. Specific examples of carbocyclic arylgroups include phenyl, indanyl, indenyl, naphthyl, phenanthryl,anthracyl, and fluorenyl. Exemplary heteroaryl groups include monocylicrings having from 1 to 4 heteroatoms selected independently from O, N,and S and from 1 to 6 carbons (e.g., C1-C6, C1-C4, and C2-C6).Monocyclic heteroaryl groups preferably include from 5 to 9 ringmembers. Other heteroaryl groups preferably include from 4 to 19 carbonatoms (e.g., C4-C10). Specific examples of heteroaryl groups includepyridinyl, quinolinyl, dihydroquinolinyl, isoquinolinyl, quinazolinyl,dihydroquinazolyl, and tetrahydroquinazolyl. Unless otherwise specified,aryl groups, used in any context herein, are optionally substituted withalkyl, alkenyl, aryl, arylalkyl, halogen, alkoxy, aryloxy, arylalkyloxy,oxo, alkylthio, alkylenedithio, alkylamino, [alkenyl]alkylamino,[aryl]alkylamino, [arylalkyl]alkylamino, dialkylamino, silyl, sulfonyl,cyano, nitro, carboxyl, or azido.

By “arylalkyl” is meant —R′R″, wherein R′ is alkylene, and R″ is aryl.

By “arylalkyloxy” is meant —OR, wherein R is arylalkyl.

By “aryloxy” is meant —OR, wherein R is aryl.

By “carboxyl” is meant —C(O)OH, in free acid, ionized, or salt form.

By “fluoride source” is meant a compound that can be a source of solublefluoride ion (i.e., F⁻) (e.g., to remove silyl ether hydroxyl protectinggroups), exemplary fluoride sources include, ammonium fluoride,benzyltriethylammonium fluoride, cesium fluoride (i.e., CsF),1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octanebis(tetrafluoroborate) (i.e., Selectfluor®), hydrofluoric acid (i.e.,HF), poly[4-vinylpyridinium poly(hydrogen fluoride)], potassium fluoride(i.e., KF), pyridine hydrogen fluoride (i.e., HF-pyridine), sodiumfluoride (i.e., NaF), tetrabutylammonium fluoride (i.e., TBAF),tetraethylammonium fluoride, tetramethylammonium fluoride, andtris(dimethylamino)sulfonium difluorotrimethylsilicate (i.e., TASF).

By “halogen” is meant fluoro, chloro, bromo, or iodo.

By “lactam” is meant a cyclic amide, wherein the ring consists of carbonatoms and one nitrogen atom.

By “leaving group” is meant a group that is displaced during a chemicalreaction. Suitable leaving groups are well known in the art, e.g., see,Advanced Organic Chemistry, March, 4th Ed., pp. 351-357, John Wiley andSons, N.Y. (1992). Such leaving groups include halogen, C1-C12 alkoxy(e.g., C1-C8, C1-C6, C1-C4, C2-C7, and C3-C6 alkoxy), C1-C12alkylsulfonate (e.g., C1-C8, C1-C6, C1-C4, C2-C7, C3-C12, and C3-C6alkylsulfonate), C2-C12 alkenylsulfonate (e.g., C2-C8, C2-C6, C2-C4,C3-C12, and C3-C6 alkenylsulfonate), carbocyclic C6-C20 arylsulfonate(e.g., C6-C15, C6-C10, C8-C20, and C8-C15 arylsulfonate), C4-C19heteroarylsulfonate (e.g., C4-C10 heteroarylsulfonate), monocyclic C1-C6heteroarylsulfonate (e.g., C1-C4 and C2-C6 heteroarylsulfonate),(C6-C15)aryl(C1-C6)alkylsulfonate,(C4-C19)heteroaryl(C1-C6)alkylsulfonate,(C1-C6)heteroaryl(C1-C6)alkylsulfonate, and diazonium. Alkylsulfonates,alkenylsulfonates, arylsulfonates, heteroarylsulfonates,arylalkylsulfonates, and heteroarylalkylsulfonates can be optionallysubstituted with halogen (e.g., chloro, iodo, bromo, or fluoro), alkoxy(e.g., C1-C6 alkoxy), aryloxy (e.g., C6-C15 aryloxy, C4-C19heteroaryloxy, and C1-C6 heteroaryloxy), oxo, alkylthio (e.g., C1-C6alkylthio), alkylenedithio (e.g., C1-C6 alkylenedithio), alkylamino(e.g., C1-C6 alkylamino), [alkenyl]alkylamino (e.g.,[(C2-C6)alkenyl](C1-C6)alkylamino), [aryl]alkylamino (e.g.,[(C6-C10)aryl](C1-C6)alkylamino, [(C1-C6)heteroaryl](C1-C6)alkylamino,and [(C4-C19)heteroaryl](C1-C6)alkylamino), [arylalkyl]alkylamino (e.g.,[(C6-C10)aryl(C1-C6)alkyl](C1-C6)alkylamino,[(C1-C6)heteroaryl(C1-C6)alkyl](C1-C6)alkylamino,[(C4-C19)heteroaryl(C1-C6)alkyl](C1-C6)alkylamino), dialkylamino (e.g.,di(C1-C6 alkyl)amino), silyl (e.g., tri(C1-C6 alkyl)silyl, tri(C6-C10aryl or C1-C6 heteroaryl)silyl, di(C6-C10 aryl or C1-C6heteroaryl)(C1-C6 alkyl)silyl, and (C6-C10 aryl or C1-C6heteroaryl)di(C1-C6 alkyl)silyl), cyano, nitro, or azido.Alkenylsulfonates can be optionally substituted with carbocyclic aryl(e.g., C6-C15 aryl), monocyclic C1-C6 heteroaryl, or C4-C19 heteroaryl(e.g., C4-C10 heteroaryl). Arylsulfonates can be optionally substitutedwith alkyl (e.g., C1-C6 alkyl) or alkenyl (e.g., C2-C6 alkenyl). Asdefined herein, any heteroaryl group present in a leaving group has from1 to 4 heteroatoms selected independently from O, N, and S. Specificexamples of suitable leaving groups include chloro, iodo, bromo, fluoro,methanesulfonate (mesylate), 4-toluenesulfonate (tosylate),trifluoromethanesulfonate (triflate, OTf), nitro-phenylsulfonate(nosylate), and bromo-phenylsulfonate (brosylate). Leaving groups mayalso be further substituted as is known in the art.

By “oxo” or (O) is meant ═O.

By “pharmaceutically acceptable salt” is meant a salt within the scopeof sound medical judgment, suitable for use in contact with the tissuesof humans and animals without undue toxicity, irritation, allergicresponse and the like and commensurate with a reasonable benefit/riskratio. Pharmaceutically acceptable salts are well known in the art. Forexample, pharmaceutically acceptable salts are described in Berge etal., J. Pharmaceutical Sciences 66:1-19, 1977 and Pharmaceutical Salts:Properties, Selection, and Use, (Eds. P. H. Stahl and C. G. Wermuth),Wiley-VCH, 2008. Representative acid addition salts include acetate,adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate,bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate,cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate,fumarate, glucoheptonate, glycerophosphate, hemisulfate, heptonate,hexanoate, hydrobromide (i.e., HBr), hydrochloride (i.e., HCl),hydroiodide (i.e., HI), 2-hydroxy-ethanesulfonate, lactobionate,lactate, laurate, lauryl sulfate, malate, maleate, malonate,methanesulfonate (i.e., mesylate), 2-naphthalenesulfonate, nicotinate,nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate,3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate,succinate, sulfate, tartrate, thiocyanate, toluenesulfonate (i.e.,tosylate), undecanoate, valerate salts and the like.

By “silyl” is meant —SiR₃, wherein each R is independently alkyl,alkenyl, aryl, or arylalkyl. Examples of silyl groups include tri(C1-C6alkyl)silyl, tri(C6-C10 aryl or C1-C6 heteroaryl)silyl, di(C6-C10 arylor C1-C6 heteroaryl)(C1-C6 alkyl)silyl, and (C6-C10 aryl or C1-C6heteroaryl)di(C1-C6 alkyl)silyl. It will be understood that, when asilyl group includes two or more alkyl, alkenyl, aryl, heteroaryl, orarylalkyl groups, these groups are independently selected. As definedherein, any heteroaryl group present in a silyl group has from 1 to 4heteroatoms selected independently from O, N, and S. Silyl groups areknown in the art, e.g., as described in Greene's Protective Groups inOrganic Synthesis, Wiley-Interscience, Edition, 2006. Specific examplesof silyl groups include trimethylsilyl (TMS), triethylsilyl (TES),t-butyldimethylsilyl (TBS), t-butyldiphenylsilyl (TBDPS),triisopropylsilyl (TIPS), and triphenylsilyl (TPS) ethers. Silyl groupsmay be substituted as is known in the art; for example, aryl andarylalkyl groups, such as phenyl, benzyl, naphthyl, or pyridinyl, can besubstituted with C1-C6 alkyl, C1-C6 alkoxy, nitro, cyano, carboxyl, orhalogen. Alkyl groups, such as methyl, ethyl, isopropyl, n-propyl,t-butyl, n-butyl, and sec-butyl, and alkenyl groups, such as vinyl andallyl, can also be substituted with oxo, arylsulfonyl, halogen, andtrialkylsilyl groups.

By “sulfonyl” is meant —S(O)₂R, wherein R is alkyl, alkenyl, aryl,arylalkyl, or silyl. In exemplary sulfonyl groups, R is C1-C12 alkyl(e.g., C1-C8, C1-C6, C1-C4, C2-C7, C3-C12, and C3-C6 alkyl), C2-C12alkenyl (e.g., C2-C8, C2-C6, C2-C4, C3-C12, and C3-C6 alkenyl),carbocyclic C6-C20 aryl (e.g., C6-C15, C6-C10, C8-C20, and C8-C15 aryl),monocyclic C1-C6 heteroaryl (e.g., C1-C4 and C2-C6 heteroaryl), C4-C19heteroaryl (e.g., C4-C10 heteroaryl), (C6-C15)aryl(C1-C6)alkyl,(C4-C19)heteroaryl(C1-C6)alkyl, or (C1-C6)heteroaryl(C1-C6)alkyl. Asdefined herein, any heteroaryl group present in a sulfonyl group hasfrom 1 to 4 heteroatoms selected independently from O, N, and S.Exemplary sulfonyl groups include tosyl, triflyl, and mesyl.

Other features and advantages of the invention will be apparent from thefollowing description and the claims.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides methods for the synthesis of halichondrinB analogs. In particular, the methods are useful for the synthesis oferibulin and pharmaceutically acceptable salts thereof:

Synthesis of Compounds of Formula (I)

Compounds of Formula (I):

can be synthesized using methods known in the art (e.g., as described inU.S. Pat. Nos. 6,214,865, 6,365,759, 6,469,182, 7,982,060, and8,148,554, International Publication Nos. WO 99/65894, WO 2005/118565,and WO 2011/094339, Chase et al. Syn. Lett. 2013; 24(3):323-326, Austadet al. Syn. Lett. 2013; 24(3):327-332, and Austad et al. Syn. Lett.2013; 24(3):333-337, the syntheses of which are incorporated herein byreference). In one example, the C14-C35 portion (e.g., ER-804028) of themolecule is coupled to the C1-C13 portion (e.g., ER-803896) to producethe C1-C35 acyclic intermediate (e.g., ER-804029), and additionalreactions are carried out to produce a compound of formula (I) (e.g.,ER-118046) as shown in Scheme 1:

Other compounds of Formula I can be produced by using differentprotecting groups in the C1-C13 and/or C14-C35 fragments.

In one specific example, deprotonation, e.g., by lithiation, of theC14-C35 sulfone fragment (i.e., ER-804028) followed by coupling to theC1-C13 aldehyde fragment (i.e., ER-803896) furnishes a mixture ofdiastereomeric alcohols (i.e., ER-804029). Additional protecting groupmanipulation and oxidation followed by removal of the sulfonyl group andan intramolecular Nozaki-Hiyama-Kishi (NHK) reaction affords anintermediate, which, when oxidized furnishes a compound of formula (I)(i.e., ER-118046).

Conversion of a Compound of Formula (I) to Eribulin

A scheme for converting a compound of formula (I) to eribulin is asfollows (Scheme 2).

As outlined in Scheme 2, deprotection of the silyl ether hydroxylprotecting groups (i.e., R¹, R², R³, R⁴, and R⁵) of a compound offormula (I) followed by equilibration furnishes ER-811475 (Step A).Ketalization of ER-811475 provides ER-076349 (Step B). Activation of theC35 primary alcohol (e.g., as the C35 tosylate) resulting in a compoundof formula (II), wherein X is a leaving group (e.g., halogen, mesylate,or tosylate) (Step C), followed by introduction of the aminefunctionality, provides eribulin (Step D). One skilled in the art wouldalso understand that variations on the above scheme are possible.

Step A: Conversion of a Compound of Formula (I) to ER-811475

Method A 1: Deprotection with Fluoride Source in THF

One method for the conversion of a compound of formula (I) to ER-811475is shown in Scheme 3:

Treatment of a compound of formula (I) with a fluoride source (e.g.,tetrabutylammonium fluoride) and equilibration with a conjugate acid ofimidazole (e.g., imidazole hydrochloride), in tetrahydrofuran assolvent, results in ER-811475 in a 4:1 mixture with its C12 stereoisomerER-811474.

Method A2: Deprotection with Fluoride Source in an Amide, e.g., DMAC

An alternative method for the conversion of a compound of formula (I) toER-811475 is shown in Scheme 4:

Treatment of a compound of formula (I) with a fluoride source (e.g.,tetrabutylammonium fluoride) and equilibration with a conjugate acid ofimidazole (e.g., imidazole hydrochloride), in an amide, e.g.,N,N-dimethylacetamide (DMAC), as solvent (e.g., a mixture oftetrahyrofuran (THF) and DMAC), results in ER-811475. The addition ofDMAC as co-solvent in the reaction results in improved selectivity atC12 (e.g., 18:1 vs. 4:1) and shortened reaction time (e.g., 1-2 daysfrom 7-10 days). The addition of the mixture of acetonitrile and waterincreases the yield of ER-811475. Other amides include an N,N C1-C6dialkyl C1-C6 alkyl amide or N C1-C6 alkyl C2-C6 lactam, such asN,N-dimethylformamide, N-methyl 2-pyrrolidone, N,N-diethylacetamide, orN,N-dimethylpropionamide may also be employed.

Step 8: Ketalization of ER-811475 to ER-076349

Method B1: Ketalization with Conjugate Acid of Pyridine

A method for the ketalization of ER-811475 is shown in Scheme 5:

Ketalization of ER-811475 (e.g., in dichloromethane) with a conjugateacid of pyridine (e.g., pyridinium p-toluenesulfonate (PPTS)), followedby crystallization from acetonitrile and water, provides ER-076349.

Method B2: Ketalization with Conjugate Acid of Imidazole

An alternative method for the ketalization of ER-811475 to ER-076349 isshown in Scheme 6:

Conversion of ER-811475 to ER-076349 can be achieved throughketalization of ER-811475 (e.g., in ethanol) with a conjugate acid ofimidazole (e.g., imidazole hydrochloride), followed by columnchromatography. Replacing PPTS with imidazole hydrochloride results in adecrease of isomerization at C12 during post-processing (e.g.,concentration of the reaction mixture). Changing of the solvent fromdichloromethane to ethanol results in a more environmentally favorableprocess.

Step C: Activation of ER-076349 to a Compound of Formula (II)

Method C1: Activation with Tosyl Chloride and Pyridine

A method for the activation of ER-076349 is shown in Scheme 7:

Reacting ER-076349 (e.g., in dichloromethane) with tosyl chloride and abase (e.g., pyridine) at 22° C. provides a compound of formula (II)(i.e., ER-082892).

Method C2: Activation with Ts₂O, Collidine, and Pyridine

An alternative method for the activation of ER-076349 is shown in Scheme8:

Treatment of ER-076349 (e.g., in dichloromethane) with 4-toluenesulfonicanhydride (Ts₂O), and base (e.g., a combination of 2,4,6-collidine andpyridine) at -10° C. provides a compound of formula (II) (i.e.,ER-082892).

Method C3: Activation with Mesyl Chloride

Another method for the activation of ER-076349 is shown in Scheme 9:

Reacting ER-076349 (e.g., in dichloromethane) with mesyl chloride and abase (e.g., 2,4,6-collidine) at 0° C. provides a compound of formula(II) (i.e., B-2294).

Method C4: Activation with Tosyl Chloride and Base

Another method for the activation of ER-076349 is shown in Scheme 10:

The activation of ER-076349 (e.g., in acetonitrile) can be achieved bytreatment (e.g., at 26 to 28° C.) with tosyl chloride and a base (e.g.,a C1-C6 trialkylamine, such as triethylamine andN,N-diisopropylethylamine) in the presence of a catalyst (e.g.,dibutyltin oxide). The use of dibutyltin oxide, for example, makes theprocess more robust (e.g., reduces reaction sensitivity to moisture) andimproves process operational efficiency (e.g., by elimination of anazeotropic drying step). Replacing pyridine and/or collidine withN,N-diisopropylethylamine and the addition of dibutyltin oxide as acatalyst provide an improvement in selectivity for primary alcohol(e.g., the mono-tosylation:di-tosylation ratio improved from 96:4 to99.8:0.2). The replacement of dichloromethane with acetonitrile assolvent results in a more environmentally favorable process, and thechange in temperature from −10° C. to 26° C.-28° C. increasesoperational efficiency and yield.

Step D: Amination of a Compound of Formula (II) to Eribulin

Method D1: Staudinger Route

A method for the amination of a compound of formula (II) is shown inScheme 11, wherein X is a leaving group (e.g., OTs):

The amination of a compound of formula (II) (e.g., ER-082892) toeribulin can be achieved through treatment with sodium azide, followedby reduction of the resulting azide with trimethylphosphine underStaudinger reaction conditions.

Method D2: Epoxide Opening Route

An alternative method for the amination of a compound of formula (II) toeribulin is shown in Scheme 12, wherein X is a leaving group (e.g.,OTs):

In this method, the amination of a compound of formula (II) (e.g.,ER-082892) can be accomplished through treatment with alcoholic ammoniumhydroxide resulting in cyclization to an epoxide in situ that reactsfurther with ammonia to provide eribulin. Replacement of the Staudingerroute with the epoxide opening route results in the elimination of theuse of hazardous reagents and an increase in operational efficiency.

Salification of Eribulin

Pharmaceutically acceptable salts of eribulin (e.g., eribulin mesylate)can be formed by methods known in the art (e.g., in situ during thefinal isolation and purification of the compound or separately byreacting the free base group with a suitable acid). In one example,eribulin is treated with a solution of methanesulfonic acid (i.e., MsOH)and ammonium hydroxide in water and acetonitrile. The mixture isconcentrated. The residue is dissolved in dichloromethane-pentane, andthe solution is added to anhydrous pentane. The resulting precipitate isfiltered and dried under high vacuum to provide eribulin mesylate, asshown in Scheme 13.

Any combination of the methods described above for the synthesis of thevarious intermediates can be utilized to convert a compound of formula(I) to eribulin (e.g., Methods A1-B2-C1-D1, A1-B2-C2-D1, A1-B2-C1-D2,A2-B1-C1-D1, A2-B2-C1-D1, A2-B1-C2-D1, A2-B1-C1-D2, A2-B2-C2-D1,A2-B2-C1-D2, A2-B1-C2-D2, A2-B2-C2-D2, A2-B1-C3-D1, A1-B2-C3-D1,A2-B2-C3-D1, A2-B1-C3-D2, A1-B2-C3-D2, A2-B2-C3-D2, A1-B1-C4-D1,A2-B1-C4-D1, A1-B2-C4-D1, A1-B1-C4-D2, A2-B2-C4-D1, A2-B1-C4-D2,A1-B2-C4-D2, and A2-B2-C4-D2,).

Experimental Procedures Step A: Conversion of ER-118046 to ER-811475Method A1:

ER-811475: (1R,2S,3S,4S,5S,6RS,11S,14S,17S,19R,21R,23S,25R,26R,27S,31R,34S)-25-[(2S)-2,3-Dihydroxypropyl]-2,5-dihydroxy-26-methoxy-19-methyl-13,20-bis(methylene)-24,35,36,37,38,39-hexaoxaheptacyclo[29.3.1.13,6.14,34.111,14.117,21.023,27]nonatriacontane-8,29-dione

The solution of ER-118046 (0.580 kg, 0.439 mol, 1 eq) in n-heptane wasconcentrated in vacuo at ≦50° C. The residue was dissolved in anhydroustetrahydrofuran (THF) (19.7 L) and treated with tetrabutyl ammoniumfluoride (TBAF) (1.0 M solution in THF, 2.85 L, 2.85 mol, 6.5 eq)buffered with imidazole hydrochloride (0.142 kg, 1.36 mol, 3.1 eq) at10-25° C. Upon confirmation of the level of C34/C35-diol (≦3%), toluene(7.6 kg) and water (8.7 kg) were added for extraction. The aqueous layerwas separated and extracted with toluene (5.0 kg) and THF (5.2 kg). Theaqueous layer was drained, and the organic layer was combined with thefirst extract. The combined organic layers were concentrated in vacuo at≦35° C. During the concentration, the free pentaol was converted toER-811475 and ER-811474. When the residual level of free pentaol was≧5%, acetonitrile (ACN) (3.3 kg) and water (0.42 kg) were added andazeotroped in vacuo <35° C. until the level came down to <5%. Uponcompletion, the residue was further azeotroped in vacuo withacetonitrile (4.6 kg)<35° C. The residue was diluted withdichloromethane (7.7 kg) and azeotroped in vacuo <35° C. to give amixture of ER-811475 and ER-811474 (4:1).

Method A2:

The solution of enone ER-118046 (135 g) in n-heptane was concentrated invacuo at 41° C. or below. The residue was dissolved in anhydroustetrahydrofuran (THF) (2.03 L) and N,N-dimethylacetamide (675 mL) andthen treated with tetrabutylammonium fluoride (TBAF) (0.97 mol/Lsolution in THF, 685 mL) buffered with imidazole HCl (31.5 g) at 16° C.to 18° C. The mixture was stirred at 16° C. to 18° C. for 47 hours, andthe reaction progress was monitored by HPLC. After the residual level ofthe reaction intermediate C34/C35-diol reached 3% or below, acetonitrile(608 mL) and water (203 mL) were added. The mixture was stirred at 16°C. to 18° C. for 45 hours until the residual level of free pentaol camedown to below 5%. The reaction mixture including ER-811475/ER-811474 (amixture of two diastereomers 18:1) could be used for the next stagewithout further purification.

Step B: Ketalization of ER-811475 to ER-076349 Method B1:

ER-076349:(1S,3S,6S,9S,12S,14R,16R,18S,20R,21R,22S,26R,29S,31R,32S,33R,35R,36S)-20-[(2S)-2,3-Dihydroxypropyl]-21-methoxy-14-methyl-8,15-bis(methylene)-2,19,30,34,37,39,40,41-octaoxanonacyclo[24.9.2.13,32.13,33.16,9.112,16.018,22.029,36.031,35]hentetracontan-24-one

ER-811475 in a mixture with ER-811474 (0.329 kg, 0.439 mol, 1 eq) wasdissolved in dichloromethane (DCM; 7.7 kg) and treated with a pyridiniump-toluenesulfonate (PPTS; 0.607 kg, 2.42 mol, 5.5 eq) solution indichloromethane (1.7 kg) at 10-20° C. The resulting mixture was stirredat 10-20° C. The major diastereomer reacted to provide diol ER-076349,and the minor diastereomer ER-811474 remained unreacted. When theresidual level of ER-811475 was >1%, additional PPTS (0.055 kg) indichloromethane (0.15 kg) was added, and the reaction was continued at10-20° C. Upon completion, the reaction mixture was directly loaded ontoa silica gel column that was pre-equilibrated with methyl t-butyl ether(MTBE) (200 L). The reactor was further rinsed with dichloromethane (3.1kg), and the rinse was loaded onto the column. The column was elutedsequentially with: (1) methyl t-butyl ether (125 L), (2) 96% v/v methylt-butyl ether in acetonitrile (125 L), (3) 50% v/v methyl t-butyl etherin acetonitrile (250 L), and (4) acetonitrile (225 L). Desired fractionswere combined, concentrated in vacuo <35° C., and azeotroped in vacuowith acetonitrile (4.6 kg) <35° C. The residue was dissolved inacetonitrile (0.32 kg) and water (0.54 kg) and subjected tocrystallization with ER-076349 seed crystals (0.27 g, 0.36 mmol) andadditional water (2.70 kg). The resulting crystals were filtered, andthe weight of the filtrate was monitored until the recovery ratio to thecrystallization solvent was reached ≧80%. The crystals were furtherwashed with water (2.7 kg) and dissolved in dichloromethane (10.8 kg),and the solution was concentrated in vacuo at ≦25° C. The residue wasdiluted with acetonitrile (2.1 kg) and concentrated in vacuo at ≦40° C.to give ER-076349 (55-75% yield from ER-118046).

Method B2:

To ER-811475 (in a mixture with ER-811474), a solution of imidazole HCl(85.5 g) in water (68 mL) was added. The solution was concentrated invacuo at 28° C. or below. The residue was dissolved in EtOH (2.69 kg).The resulting mixture was stirred at 21° C. to 24° C. for 43 hours. Themajor diastereomer (ER-811475) reacted to provide diol ER-076349, andthe minor diastereomer (ER-811474) remains unreacted. The reaction wasmonitored for a disappearance of ER-811475 by HPLC. After the residuallevel of ER-811475 reached below 1%, the solution was concentrated invacuo at 37° C. or below. Toluene (1.35 L) was added, and the solutionwas azeotroped in vacuo at 37° C. or below. Tetrahydrofuran (THF) (4.20kg), toluene (1.76 kg), and water (2.03 L) were added and extracted. Theaqueous layer was separated, and the organic layer was washed with water(1.01 L). The aqueous layers were combined and extracted with toluene(1.18 kg) and THF (1.20 kg). The aqueous layer was drained, and theorganic layer was combined with the first extract. The combined organiclayers were concentrated in vacuo at 37° C. or below. Toluene (675 mL)was added, and the solution was azeotroped in vacuo at 38° C. or below.The concentrate was diluted with dichloromethane (1.01 L) and thenloaded onto a silica gel column (5.511 kg) pre-equilibrated with methylt-butyl ether (more than 55.1 L). The column was eluted sequentiallywith methyl t-butyl ether (40.8 L), 95% v/v methyl t-butyl ether inacetonitrile (24.9 L), 40% v/v methyl t-butyl ether in acetonitrile(83.6 L), and acetonitrile (76.3 L) to remove the unreactedintermediates, the reaction impurities, and the carryover impuritiesfrom ER-804028. Desired fractions were combined and concentrated invacuo at 32° C. or below to give ER-076349 (assay 62.02 g, yield overtwo steps 84.0%). The residue was azeotroped in vacuo with acetonitrile(0.533 kg) at 29° C. or below and could be used for the next stagewithout further purification.

Steps C and D: Conversion of ER-076349 to Eribulin: Methods C2+D2:

eribulin:(1S,3S,6S,9S,12S,14R,16R,18S,20R,21R,22S,26R,29S,31R,32S,33R,35R,36S)-20-[(2S)-3-Amino-2-hydroxypropyl]-21-methoxy-14-methyl-8,15-bis(methylene)-2,19,30,34,37,39,40,41-octaoxanonacyclo[24.9.2.13,32.13,33.16,9.112,16.018,22.029,36.031,35]hentetracontan-24-one

ER-076349 (0.259 kg, 0.354 mol, 1 eq) was dissolved in toluene (4.7 kg)and azeotroped in vacuo at <25° C. The residue was diluted with toluene(4.5 kg) to give a toluene solution for monitoring of water content.Water content was measured by Karl-Fischer (KF) titration method. If theKF value was >125 ppm, the solution was azeotroped in vacuo at <25° C.and diluted with toluene (4.5 kg) until the water content came down to≦125 ppm. If the KF value reached the target value, the solution wasconcentrated and dissolved in anhydrous dichloromethane (6.5 kg).2,4,6-collidine (0.172 kg, 1.27 mol, 4 eq) and pyridine (0.0014 g, 0.018mol, 0.05 eq) in anhydrous dichloromethane (84.1 g) were added, and themixture was cooled. A solution of Ts₂O (0.124 kg, 0.380 mol, 1.07 eq) inanhydrous dichloromethane (3.4 kg) was added to the reaction mixture ata rate to maintain the reaction temperature at ≦−10° C., and the mixturewas stirred at ≦−10° C. When the residual amount of ER-076349 was <3% orthe generation of corresponding bis-tosylate was more than 4%, thereaction mixture was quenched by the addition of water (1.0 kg). Themixture was warmed up, and then isopropyl alcohol (IPA) (20.5 kg) andammonium hydroxide (NH₄OH; 25.7 kg) were added consecutively at 10-30°C. Upon complete consumption of the epoxide (target ≦0.85%; add extraNH₄OH if necessary), the reaction mixture was concentrated in vacuo at<30° C. To the residue, dichloromethane (20.7 kg) and a sufficientamount of buffer solution of NaHCO₃/Na₂CO₃/water (9/9/182 w/w/w; notmore than 5.166 kg) were added and extracted. The organic layer wasseparated, and the aqueous layer was extracted with dichloromethane (8.6kg). The organic layer was separated and combined with the firstextract. The combined organic layers were concentrated in vacuo at <30°C. The concentrate was diluted with acetonitrile (4.0 kg) and thenloaded onto silica gel column which was preequilibrated withacetonitrile (200 L). The column was eluted sequentially with: (1)acetonitrile (100 L), (2) 90.0/7.5/2.5 v/v/v acetonitrile/water/200 mMaqueous NH₄OAc (152.4 L), (3) 85.8/11.7/2.5 v/v/v acetonitrile/water/200mM aqueous NH₄OAc (152.4 L), (4) 83.5/14.0/2.5 v/v/vacetonitrile/water/200 mM aqueous NH₄OAc (152.6 L), and (5)80.0/17.6/2.4 v/v/v acetonitrile/water/200 mM aqueous NH₄OAc (>100.2 L).Desired fractions were combined and concentrated in vacuo at ≦40° C.while maintaining the internal pH at 5.5-9.0 by adding NH₄OH. To theresidue, dichloromethane (13.9 kg) and a sufficient amount of buffersolution of NaHCO₃/Na₂CO₃/water (9/9/182 w/w/w; not more than 15.51 kg)were added and extracted. The organic layer was separated, and theaqueous layer was extracted with dichloromethane (8.7 kg). The organiclayer was separated and combined with the first extract. The combinedorganic layers were concentrated in vacuo at <30° C. The residue wasdissolved in 75% v/v anhydrous dichloromethane in n-pentane (6.12 kg)and filtered. The filtrate was concentrated in vacuo at <30° C., dilutedwith acetonitrile (2.1 kg), and concentrated in vacuo at ≦35° C. to giveeribulin (75-95% yield).

Methods C3+D1:

MsCl (0.3 M in CH₂Cl₂, 98 μL, 0.030 mmol) was added dropwise over 40 minto a mixture of 2,4,6-collidine (7 μL, 0.054 mmol), ER-076349 (20.8 mg,0.028 mmol), and CH₂Cl₂ (1 mL) at 0° C. After 76 h at 4° C., thereaction was quenched with a 1:4 mixture of saturated aqueousNaHCO₃-brine and extracted with CH₂Cl₂ (4×). The combined extracts weredried over Na₂SO₄ and concentrated. The crude product was dissolved intoluene (3 mL), concentrated, and purified by preparative TLC (1.5%MeOH-EtOAc) to afford mesylate B-2294 (21.4 mg, 95%).Tetra-n-butylammonium azide (0.2 M in dimethylformamide, 0.5 mL, 0.10mmol) was added to a solution of mesylate B-2294 (21.4 mg, 0.026 mmol)in dimethylformamide (2 mL) at room temperature and warmed to 83° C.After stirring at 83° C. for 3.5 h, the reaction mixture was cooled toroom temperature, diluted with toluene, concentrated and purified bypreparative TLC (80% ethyl acetate-hexanes) to furnish B-1922 (18 mg,92%). Me₃P (1 M in tetrahydrofuran) and H₂O (0.8 mL) were sequentiallyadded to a solution of azide B-1922 (24.6 mg, 0.032 mmol) in THF (3.2mL) at room temperature. The mixture was stirred for 22 h, diluted withtoluene, concentrated and purified by flash chromatography [stepgradient, 10% MeOH-EtOAc followed by MeOH-EtOAc-30% aqueous NH₄OH(9:86:5)] to provide the desired primary amine (23.3 mg), which by¹H-NMR contained ˜1% trimethylphosphine oxide. Lyophilization frombenzene and standing under high vacuum for 2 d furnished eribulin (20.3mg, 87%).

Methods C4+D2:

The diol ER-076349 (58.3 g) was dissolved in acetonitrile (935 mL). Asuspension of dibutyltin oxide (0.99 g) and N,N-diisopropylethylamine(28.5 mL) in acetonitrile (117 mL) were added. A solution of TsCl (30.5g) in acetonitrile (117 mL) was added to the reaction mixture at a rateto maintain the reaction temperature at 26° C. to 28° C., and themixture was stirred at 26° C. to 28° C. The reaction was monitored byHPLC for consumption of ER-076349. After the residual level of ER-076349reached below 3% and reaction time passed over 27 hours, isopropylalcohol (IPA) (4.58 kg) and ammonium hydroxide (5.82 kg) were addedconsecutively at 15° C. to 20° C. The mixture was stirred at 15° C. to20° C. for 66 hours, and the reaction was monitored by HPLC for aconsumption of reaction intermediate ER-809681. After the residual levelof ER-809681 reached 0.85% or less, the reaction mixture wasconcentrated in vacuo at 29° C. or below. To the residue,dichloromethane (4.64 kg) and a sufficient amount of buffer solution ofNaHCO₃/Na₂CO₃/water (9/9/182 w/w/w) (530 mL) were added and extracted.The organic layer was separated, and the aqueous layer was extractedwith dichloromethane (1.94 kg). The organic layer was separated, andcombined with the first extract. The combined organic layers wereconcentrated in vacuo at 25° C. or below. The concentrate was dilutedwith acetonitrile (1.17 L), and then loaded onto silica gel column(5.511 kg) which was pre-equilibrated with acetonitrile (more than 55.1L). The column was eluted sequentially with acetonitrile (29.6 L),90.0/7.5/2.5 v/v/v acetonitrile/water/200 mM aqueous NH₄OAc (46.2 L),85.8/11.7/2.5 v/v/v acetonitrile/water/200 mM aqueous NH₄OAc (45.8 L),83.5/14.0/2.5 v/v/v acetonitrile/water/200 mM aqueous NH₄OAc (46.5 L),80.0/17.6/2.4 v/v/v acetonitrile/water/200 mM aqueous NH₄OAc (29.8 L) toremove the unreacted intermediates and the reaction impurities. Desiredfractions were combined and concentrated in vacuo at 36° C. or belowwhile maintaining the internal pH at 5.5 to 9.0 by adding ammoniumhydroxide. To the residue, dichloromethane (3.98 kg) and a sufficientamount of buffer solution of NaHCO₃/Na₂CO₃/water (9/9/182 w/w/w) (2.02kg) were added and extracted. The organic layer was separated, and theaqueous layer was extracted with dichloromethane (2.48 kg). The organiclayer was separated and combined with the first extract. The combinedorganic layers were concentrated in vacuo at 24° C. or below. Theresidue was dissolved in 75% v/v anhydrous dichloromethane in n-pentane(1.03 L) and filtered. The filtrate was concentrated in vacuo at 25° C.or below to give eribulin. The residue was diluted with acetonitrile(392 mL) and dichloromethane (69 mL) to give eribulinacetonitrile/dichloromethane solution (assay 49.11 g, corrected yield85.3%). The solution was concentrated in vacuo at 29° C. or below andused for the next stage.

Salification of Eribulin Salification to Eribulin Mesylate:

eribulin mesylate:(2R,3R,3aS,7R,8aS,9S,10aR,11S,12R,13aR,13bS,15S,18S,21S,24S,26R,28R,29aS)-2-[(2S)-3-Amino-2-hydroxypropyl]-3-methoxy-26-methyl-20,27-dimethylidenehexacosahydro-11,15:18,21:24,28-triepoxy-7,9-ethano-12,15-methano-9H,15H-furo[3,2-i]furo[2′,3′:5,6]pyrano[4,3-b][1,4]dioxacyclopentacosin-5(4H)-onemethanesulfonate

ER-086526-00 (46.68 g) was dissolved in acetonitrile (591 mL) and water(31 mL) and treated with a solution of methanesulfonic acid (MsOH, 4.09mL) and NH₄OH (187 mL) in acetonitrile (624 mL). The mixture wasconcentrated in vacuo at 24° C. or below and azeotroped repeatedly withanhydrous acetonitrile (234 mL) in vacuo at 24° C. or below to removewater. The residue was dissolved in 75% v/v anhydrous dichloromethane inn-pentane (1.10 L) and filtered. The filtrate was concentrated in vacuoat 24° C. or below. The residue was dissolved in 50% v/v anhydrousdichloromethane in n-pentane (1.16 L), and the solution was transferredthrough a filter to anhydrous pentane (3.26 kg) in the separate reactor.The resulting precipitate was stirred for 29 hours. The precipitateswere filtered, washed with n-pentane (2.92 kg), and dried under nitrogenflow in vacuo until the residual solvent levels reached the targetnumbers: n-pentane ≦25000 ppm; 2-methylbutane ≦1000 ppm;2,2-dimethylbutane ≦1000 ppm; and cyclopentane ≦1000 ppm. After drying,the precipitates were mixed in vacuo to give eribulin mesylate (gross45.95 g, corrected yield 83.8%). The drug substance was filled in apolytetrafluoroethylene (PTFE) bottle. The PTFE bottle was packed in analuminum laminate bag.

Other Embodiments

Various modifications and variations of the described methods of theinvention will be apparent to those skilled in the art without departingfrom the scope and spirit of the invention. Although the invention hasbeen described in connection with certain embodiments, it should beunderstood that the invention as claimed should not be unduly limited tosuch embodiments. Indeed, various modifications of the described modesfor carrying out the invention that are obvious to those skilled in therelevant art are intended to be within the scope of the invention.

What is claimed is:
 1. A method of preparing an intermediate in thesynthesis of eribulin, said method comprising reacting a compound havingformula (I):

wherein each of R¹, R², R³, R⁴, and R⁵ is independently a silyl group,with a fluoride source in a solvent comprising an amide to produce theintermediate ER-811475:


2. The method of claim 1, wherein the intermediate ER-811475 is producedin a mixture with an intermediate ER-811474:


3. The method of claim 2, further comprising adding a mixture ofacetonitrile and water.
 4. The method of any one of the precedingclaims, wherein each of R¹, R², R³, R⁴, and R⁵ is t-butyldimethylsilyl.5. The method of any one of the preceding claims, wherein the fluoridesource is tetrabutylammonium fluoride.
 6. The method of any one of thepreceding claims, wherein the solvent further comprises tetrahydrofuran.7. The method of any one of the preceding claims, wherein the amide isan N,N C1-C6 dialkyl C1-C6 alkyl amide or N C1-C6 alkyl C2-C6 lactam. 8.The method of any one of the preceding claims, wherein the amide isN,N-dimethylacetamide, N,N-dimethylformamide, N-methyl 2-pyrrolidone,N,N-diethylacetamide, or N,N-dimethylpropionamide.
 9. A method ofpreparing an intermediate in the synthesis of eribulin, said methodcomprising reacting ER-811475:

with a conjugate acid of imidazole to produce the intermediateER-076349:


10. The method of claim 9, wherein the reacting occurs in ethanol. 11.The method of claim 9 or 10, wherein the conjugate acid is imidazolehydrochloride.
 12. The method of any one of claims 9-11, whereinER-811475 is produced by the method of any one of claims 1-8.
 13. Amethod of preparing an intermediate in the synthesis of eribulin, saidmethod comprising reacting ER-076349:

with a sulfonylating reagent in the presence of a metal catalyst toproduce the intermediate:

wherein R6 is sulfonyl.
 14. The method of claim 13, wherein thesulfonylating reagent is tosyl chloride.
 15. The method of claim 13 or14, wherein the reacting occurs in acetonitrile.
 16. The method of anyone of claims 13-15, wherein said metal catalyst is dibutyltin oxide.17. The method of any one of claims 13-16, wherein the reacting occursabove 0° C.
 18. The method of any one of claims 13-17, wherein ER-076349is produced by the method of any one of claims 9-12.
 19. A method ofproducing eribulin, said method comprising the steps of: a) producing anintermediate ER-811475:

by the method of any one of claims 1-8; b) ketalizing intermediateER-811475 to produce the intermediate ER-076349:

and c) aminating ER-076349 to produce eribulin:


20. The method of claim 19, further comprising salifying eribulin toproduce a pharmaceutically acceptable salt of eribulin.
 21. The methodof claim 20, wherein said salt is the mesylate salt.
 22. The method ofany one of claims 19-21, wherein ER-076349 is produced by the method ofany one of claims 9-11.
 23. The method of any one of claims 19-22,wherein step c) comprises converting ER-076349 to ER-082892:

according to the method of any one of claims 13-17.
 24. A method ofproducing eribulin, said method comprising the steps of: a) producingthe intermediate ER-076349:

by the method of any one of claims 9-11; and b) aminating ER-076349 toproduce eribulin:


25. The method of claim 24, further comprising salifying eribulin toproduce a pharmaceutically acceptable salt of eribulin.
 26. The methodof claim 25, wherein said salt is the mesylate salt.
 27. The method ofany one of claims 24-26, wherein step b) comprises converting ER-076349to ER-082892:

according to the method of any one of claims 13-17.
 28. A method ofproducing eribulin, said method comprising the steps of: a) producingthe intermediate ER-082892:

by the method of any one of claims 13-17; and b) aminating ER-082892 toproduce eribulin:


29. The method of claim 28, further comprising salifying eribulin toproduce a pharmaceutically acceptable salt of eribulin.
 30. The methodof claim 29, wherein said salt is the mesylate salt.
 31. A method ofmanufacturing a pharmaceutical product comprising eribulin or apharmaceutically acceptable salt thereof comprising: a) producing ordirecting the production of eribulin or a pharmaceutically acceptablesalt thereof by the method of any one of claims 19-30; and b) processingor directing the processing of eribulin or a pharmaceutically acceptablesalt thereof into a pharmaceutical product comprising eribulin or apharmaceutically acceptable salt thereof; thereby manufacturing apharmaceutical product comprising eribulin or a pharmaceuticallyacceptable salt thereof.
 32. The method of claim 31, wherein said saltis the mesylate salt.
 33. The method of claim 31 or 32, wherein theprocessing step comprises one or more of: formulating eribulin or apharmaceutically acceptable salt thereof; processing eribulin or apharmaceutically acceptable salt thereof into a drug product; combiningeribulin or a pharmaceutically acceptable salt thereof with a secondcomponent; lyophilizing eribulin or a pharmaceutically acceptable saltthereof; combining a first and second batch of eribulin or apharmaceutically acceptable salt thereof to provide a third largerbatch; disposing eribulin or a pharmaceutically acceptable salt thereofinto a container; packaging eribulin or a pharmaceutically acceptablesalt thereof; associating a container comprising eribulin or apharmaceutically acceptable salt thereof with a label; or shipping ormoving eribulin or a pharmaceutically acceptable salt thereof to adifferent location.